The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a metallizing process for a semiconductor device.
In an integrated circuit manufacturing process, the stressed point, after main parts of hundreds of thousands of transistors have been completed, is to interconnect them to present an integral electronic device. The process to so interonnect is generally referred to as a metallizing process.
For a semiconductor metallizing process, aluminum is the most popularly used material for the device runner. When the integration of the semiconductor device becomes higher an d higher, it would be difficult to use an aluminum-based runner again in that silicon exists a specific solid solubility with respect to aluminum and that the interface between silicon and aluminum will easily result in a spiking phenomenon through interdiffusion in a relatively high temperature to cause a poor contact between aluminum wire and MOS transistor. In addition, when the breadth of the aluminum becomes narrower as the device becomes smaller, the aluminum atom is caused to move by electromigration to result in an open state of the aluminum wire.
Accordingly, the present semiconductor manufacturing process adopts the aluminum alloy, e.g. AlCu alloy to serve as the conducting material for the semiconductor device. In order to further realize the metallization in the known technique, in FIGS. 1Axcx9c1D, we use the AlCu alloy serving as the conducting material to illustrate the metallizing process and shortcomings according to the prior art.
FIG. 1A schematically shows the following steps of providing a silicon substrate 11, forming on silicon substrate 11 by DC sputtering an AlCu alloy layer 12 having a thickness of about 5,000 xc3x85xcx9c10,000 xc3x85, and forming on AlCu alloy 12 a titanium nitride (TiN) layer 13 having a thickness of about 200 xc3x85xcx9c1500 xc3x85 by reactive DC sputtering. It is to be noticed that in the general metallizing process for the semiconductor device, the metal layer is provided thereon with an anti-reflection layer of a conducting material in order to avoid a pattern transfer error in the photolithography process. As such, the purpose of forming titanium nitride (TiN) layer 13 is to prevent the surface of AlCu alloy 12 layer from reflection in order to secure the exposure exactitude for the subsequent photolithography process. Thus, the device runner is consisted of AlCu layer 12 and titanium nitride (TiN) layer 13. Since the material property of titanium nitride (TiN) layer 13 is hard and the curvature of the chip surface in the semiconductor process is not the same, titanium nitride (TiN) layer 13 is extremely prone to crack to form a crack 131 as shown in FIG. 1A.
After the anti-reflection titanium nitride (TiN) layer 13 is formed on AlCu layer 12, there are proceeded with photolithography and etching processes. The photoresist developer, e.g. the alkaline solution of sodium hydroxide (NaOH) or potassium hydroxide (KOH), the etching solution, e.g. a solution using the chloride as the primary reacting gas, or the washing agent used in the washing process will leak through crack 131. Since there exists an oxidizing potential difference between titanium nitride (TiN) layer 13 and AlCu alloy layer 12, there will be resulted in a local spontaneous electrochemical reaction, just like the function of a galvanic cell, to have an equivalent circuit diagram as shown in FIG. 1D where titanium nitride layer 13 serves as an anodic plate 14 and AlCu alloy layer 12 serves as a cathodic plate 15 in the concerned circuit. The spontaneous electrochemical reaction between two electrode plates 14, 15 converts the chemical energy into the electric energy. In addition to consume the material of AlCu alloy layer 12, the spontaneous electrochemical reaction will leave an unetchable by-product beneath AlCu alloy layer 12. The by-product, as shown in FIG. 1B, is an aluminum oxide (Al2O3) 121 having a thickness of about 30 xc3x85xcx9c50 xc3x85. This aluminum oxide 121 cannot be removed by the etching chloride plasma etching titanium nitride layer 13 and AlCu alloy layer 12.
Accordingly, the device runner having been subjected to an etching process will present an etched result as shown in FIG. 1C. Specifically, the AlCu alloy layer 12 right beneath aluminum oxide 121 will not be etched away and will present an AlCu alloy residue 122. AlCu alloy residue 122 will primarily explain why the runner of AlCu alloy layer 12 is short-circuited. Furthermore, since AlCu alloy layer 12 will be undesiredly partly etched away, it is impossible to obtain a correct runner-etching result to seriously adversely influence the required short-circuiting condition between device runners which should be overcome as soon as possible.
It is therefore tried by the Applicant to deal with the above situation encountered in the prior art.
It is therefore an object of the present invention to provide a process for metallizing a semiconductor device without an etching residue.
It is further an object of the present invention to provide a process for metallizing a semiconductor device having a desired runner pattern.
It is additional an object of the present invention to provide a process for metallizing a semiconductor device having a relatively high yield rate.
According to the present invention, a process for metallizing a semiconductor device comprising the steps of a) providing a semiconductor substrate, b) forming a conductive layer on the semiconductor substrate, c) forming a dielectric layer on the conductive layer, d) forming a titanium nitride layer directly on the dielectric layer without contacting the conductive layer, and e) patternizing the titanium nitride layer, the dielectric layer and the conductive layer, wherein the dielectric layer is used for avoiding spontaneous electrochemical reaction between the titanium nitride layer and the conductive layer.
Certainly, the step b) can be executed by a reactive DC sputtering. The conductive layer can be a metal layer which can be made of an AlCu alloy. The conductive layer can have a thickness ranged from 5,000 xc3x85xcx9c10,000 xc3x85. The step c) can be executed by oxidation.
Further, the dielectric layer can be an oxide layer which can be an aluminum oxide (Al2O3) layer having a thickness ranged from 10 xc3x85 to 20 xc3x85, or a silicon dioxide (SiO2) layer having a thickness ranged from 10 xc3x85 to 50 xc3x85.
Certainly, the step c) can be executed by nitridation. The dielectric layer can be a nitride layer which can be an aluminum nitride (AlN) having a thickness ranged from 10 xc3x85 to 50xc3x85.
Still more, the step d) can be executed by a reactive DC sputtering. The titanium nitride (TiN) layer can have a thickness ranged from 200 xc3x85xcx9c1,500 xc3x85.
Preferably the step e) further includes the following sub-steps of e1) executing a photolithography process according to a specific runner pattern to cover a photoresist layer on the titanium nitride layer, e2) executing a first etching process to etch away portions of the titanium nitride layer, the dielectric layer and the conductive layer not covered by the photoresist layer, and e3) executing a second etching process to etch away the photoresist layer, the titanium nitride layer and the dielectric layer.
The present invention may best be understood through the following descriptions with reference to the accompanying drawings, in which: